Experimental tonography on enucleated human eyes. I. The validity of Grant's tonography formula

When newer tables for parameters in Grant's formula for tonography are used, one obtains far higher values for the outflow facility than those generally accepted. The aim of this iinvestigation has, therefore, been to test the validity of the tonography formula. The outflow facility determined by constant-rate perfusion in enucleated eyes has been compared with the results of tonography on the same eyes in the steady-state condition. Loss of intraocular fluid during tonography has been measured directly by means of a new technique. Outflow facilities determined according to the two methods show very good agreement. Thus, when the production of aqueous is held at a constant rate, and when there is no change in intraocular blood volume. Grant's tonography formula is found valid, provided absolute values for Po, Pt, and dV are used.